Various arrangements are known in the art for controlling the loading and emptying of liquid from a multi-compartmented transportation tank. U.S. Pat. No. 2,453,413, issued Nov. 9, 1948, in the name of Joseph H. DeFrees and entitled Valve Structure; U.S. Pat. No. 2,557,177 issued June 19, 1951 in the name of Joseph H. DeFrees and entitled Valve Structure, and U.S. Pat. No. 3,558,097 issued Jan. 26, 1971 in the name of Joseph H. DeFrees, and entitled Valve are examples of prior art arrangements for controlling flow of inflammable liquids in connection with a multi-compartmented transportation tank vehicle.
In addition to the usual controllable valve provided at the discharge outlet of each compartment of a multi-compartmented tank, there is also usually provided in liquid flow sequence therewith, an additional valve commonly termed an "emergency" valve. The emergency valve is generally located in a relatively inaccessible portion of the tank compartment bottom, so as to be protected somewhat from shock or injury in the event of an accident to the tank. Such emergency valve in each compartment of the multi-compartmented tank is normally closed so that the valve conduit connections external thereto may suffer damage without liquid discharge from the tank.